Polyamidoamine resins (PAE resins) have been used as additives in the manufacture of paper having high levels of wet strength. See e.g., U.S. Pat. Nos. 2,926,116 and 2,926,154. PAE resins have also been used as adhesives in the creping process for producing tissue and towel paper products. See e.g., U.S. Pat. No. 5,338,807 and Canadian Patent No. 979,579. Numerous other polymers and combinations of polymers have been used as adhesives in the process of creping tissue and towel grades of paper.
Cationic polyamidoamines crosslinked with a multi-functional aldehyde have been disclosed, See e.g., U.S. Pat. No. 5,382,323. Creping adhesives based on an admixture of PAE resins have also been disclosed, as have highly branched PAE resins having high molecular weight and procedures for making them. See e.g., U.S. Pat. Nos. 5,382,323; 5,786,429; and 5,902,862.
PAE resins are typically made by a two-step process. In the first step a polyamidoamine is synthesized by the polycondensation of near-equimolar quantities of a diacid and a polyamine (e.g., adipic acid and diethylenetriamine (DETA)). In the second step, the polyamidoamine is reacted with a difunctional crosslinker, such as epichlorohydrin, in aqueous solution. When producing wet strength resins the ratio of epichlorohydrin to the amine groups of the polyamidoamine is close to equimolar. Creping adhesives are generally made with an epichlorohydrin/amine ratio of less than 1.00, and typically in a ratio in the range of from 0.05 to 0.50.
Preparation of PAE Wet Strength Resins Made from Polyamidoamines that were Prepared with an excess of polyalkylenepolyamine have also been described. See e.g., U.S. Pat. Nos. 4,287,110; 4,336,835; and 5,017,642. High solids PAE wet strength resins made from polyamidoamines that were prepared with an excess of polyalkylenepolyamine has also been disclosed. See e.g., U.S. Pat. No. 6,908,983, which also discloses PAE creping adhesives made from polyamidoamines prepared with an amine excess.
Although a wide range of chemistry has been developed for creping applications, there still exists a need for improved adhesive products to be used in the creping process and improved processes for making such products. In particular, adhesives that will provide good creping performance under conditions of high temperature and/or low sheet moisture are quite desirable. Surprisingly, it has been found that creping adhesives prepared according to the processes of the present invention provide superior high temperature performance when compared to other creping adhesives.